The present invention relates to a cut sheet feeding mechanism for use in a printer, typewriter or the like, and more particularly to a cut sheet feeding mechanism for separating a cut sheet from stacked cut sheets in a sheet hopper and for feeding it to a printing position of a printing apparatus.
Such a conventional sheet feeding mechanism is disclosed in U.S. Pat. No. 4,248,415 patented to Steinhilber on Feb. 3, 1981. This mechanism includes a pick-up roller for picking up a cut sheet from a sheet hopper and for feeding it to a platen roller on which the printing operation is carried out. The platen roller is connected to a drive motor and rotated by the drive motor in a first direction to feed the cut sheet in cooperation with a pressure roller urged to a surface of the platen roller during the printing operation. The pick-up roller also obtains its rotary force from the drive motor thru a transmission which includes gears, a belt and a one-way clutch.
In operation, first, the drive motor enables the platen roller to rotate in a second direction reverse to the first direction in order to pick up a cut sheet from the sheet hopper. The transmission transmits the rotary force to the pick-up roller so as to rotate the pick-up roller in the first direction. Thus, the pick-up roller picks up the uppermost sheet in the sheet hopper and feeds it to a contact portion between the platen roller and the pressure roller. After the leading edge of the cut sheet has been fed to and pressed against the contact portion, the drive motor then rotates in the reverse direction, enabling the platen roller to rotate in the first rotary direction to feed the cut sheet to the printing position. The one-way clutch prevents the transmission of the rotary force in this direction to the pick-up roller. Accordingly, the rotation of the pick-up roller is stopped so as not to interrupt the feeding of the cut sheet by the platen roller and the pressure roller.
In the conventional mechanism, the leading edge of the cut sheet is pressed by the pick-up roller against the contact portion where the pressure roller is urged against the platen roller, which rotates in the second direction, before the platen roller feeds the cut sheet to the printing position. Accordingly, the leading edge of the cut sheet is apt to be bent by the reverse feeding force of the platen roller, and moreover, forced out of the contact portion.